Embodiments described herein relate to a filter and an X-ray imaging apparatus, and more particularly to a filter that adjusts energy spectra of X-ray, and an X-ray apparatus provided with the filter.
A X-ray imaging apparatus irradiates X-ray to a subject by adjusting energy spectrum of the X-ray with a filter. The filter is provided in a collimator box attached to an X-ray tube. In order to obtain desired spectrum, the filter can be used by switching multiple filter plates which are attached to a rotating disc, as disclosed in the Japanese Patent Application No. HEI11-76219. In this prior art, the energy spectrum can be adjusted in a wide range according to the actual needs, but in the construction in which the filter plates are switched by the rotating disc, a four-step adjustment is about all this construction can provide. Therefore, widening the adjustment range causes a rough step, while providing more steps narrows the adjustment range. When a multi-step adjustment is made possible in the rotating disc system anyway, the rotating disc to which a great number of filters are attached is increased in size, thus unrealistic.
In addition, the U.S. Pat. No. 7,260,183 reveals a filter which is provided with a cam having a curve to adjust laminated filter plates, in order to realize a filter that can make a fine spectrum adjustment in a wide rage and can be miniaturized. However, there are some disadvantages in the technical solution of this prior art: 1. when there are more than two cams in a set of cams, the curve becomes very complex and thus the cam will be in an execrable stressed state, even the angle of the force driving the cam is approximate to the angle of friction. When the cam is rotated to a certain direction or to a certain state, it will be in a more execrable stressed state; 2. since one driving system will drive at most two filter plates in practice, more driving systems are needed to drive two or more filter plates, and thus the disadvantages of high cost, large size and complex structure are caused.